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Processing with StarTools

1. Overview The Lens module allows for correcting some of the common lens and mirror aberrations and defects such as some types of chromatic aberration and coma Chromatic aberration is the phenomenon of different wavelengths colours of light coming to focus at slightly different distances Chromatic aberration is usually prevalent in cheaper lens systems but even the most expensive optical systems suffer from a minute amount of chromatic aberration The Lens module can correct for some of the ill effects of lateral or transverse chromatic aberration This type chromatic aberration often takes the form of unwanted colour fringes progressively getting worse towards some or all corners of the image Please note that the Lens module does not correct for axial or longitudinal chromatic aberration This type of chromatic aberration is often the cause of blue or purple halos around stars To correct for this type of chromatic aberration please refer to the Boost module chapter and example page 85 Coma is an inherent property of telescopes using parabolic mirros Light from a point source such as a Star in the center of the field is perfectly focused at the focal point of the mirror However when the light source is off center off axis the different parts of the mirror do not reflect the light to the same point This results in a point of light that is not in the center of the field looking wedge shaped The further off axis the
2. StarTools 1 0 26 User Manual There are as many schools of astroimage processing as there are astrophotographers Rogelio Bernal Andreo Astrophotographer DeepSkyColors com Last updated 20 March 2011 Copyright 2011 SiliconFields All Rights Reserved Please contact us through our website at http www startools org if you find any mistakes factual errors or copyright usage violations in this manual StarTools 1 0 User Manual Table of Contents O a e aE A A E anomie 7 Getting Started and system FEQUIEEMIENIS a 8 Processing with Star OOS iin asc A A ES 10 An address to beginners and advanced USETS c ccesccesseeseceeeeeeseceseeeeeeceseeeeeeceseeeeeeeeeeeeeeeenaas 10 Making your data Star Tools Mendivil women 11 What StarTools does and does not dO ni A A A AS 11 Mtra A 13 Mod ii a A ds 16 WIP alle 19 O o cos ae e o e a 19 US E NN AN ada 22 COIE O SI A re nn eee 27 A etanol 27 E O E 28 CONS A A a a A aa 30 O A A tas 30 A E RENO 31 ERGOBIA rar PEP OCP SIT OS en NTT RE PEA TEU EO SER ERE 34 A eee a ea 34 Me deb dos do 35 O ees 37 Os EEEE E 37 A E E ON 38 LEnS ense A aTa aE E E R AR E E E ea aaa he tis E aE 42 OVEVIEW aar n ae er id 42 VSADE oneens EE E o O 43 ED aiD DE NEEE ROWE AEA AS SR O 45 OVVIE Warre yht eae E A N te alt e 45 DNs O 45 StarTools 1 0 User Manual SO A O 46 Telesc op Mad A SD airia 46 A OS 50 Examining an Ontur da E AA AS 54 The ethics of using synthesised compo
3. algorithm 66 StarTools 1 0 User Manual Sharp A sharpening tool is an important tool in any astrophotographer s toolbox It emphasises details in an image that would otherwise be hard to notice StarTools Sharp module offers a selection of 4 algorithms to sharpen your image with along with several other features that can be used in conjunction to improve your results even more 3 of the available algorithms ST Sharp ST Definition and ST Hybrid were specifically designed from the ground up for astronomical use and you will not find these anywhere else When you think of sharpening you typically think of revealing fine detail While the Sharp module is certainly more than capable of this the Sharp module goes much further the Sharp module can be made scale aware Scale aware sharpening allows you to control the size of the features that you wish to sharpen For instance you can now make the spiral arms in a galaxy stand out without sharpening any further details that are smaller or larger In some ways this makes StarTools Sharp module very similar to traditional Wavelet sharpening however Wavelet sharpening forces feature size ranges octaves upon the user whereas the Sharp module lets the user freely choose a continuum of feature sizes that the user wishes to work on The Sharp module may also function as a scale decomposition tool being able to selectively remove or attenuate features of a particu
4. sees that part boosted o Pass retains the selected spectral line and diminishes all others This feature is particularly useful for isolating features that correspond to a spectral line These can then be processed separately and recombined with the original image at a later stage by using the Layer module 81 StarTools 1 0 User Manual Boost fa StarTools 2 Cancel Reset Undo Mask Keep Help Before A ag e e StarTools Illustration 42 Clicking on the yellow region of the spectrum with Filter Mode set to Pass attenuates all other parts of the spectrum while keeping the yellow part intact o Reject attenuates the selected spectral line and retains all others This feature is particularly useful for isolating features that are otherwise drowned out by a specific spectral line 82 StarTools 1 0 User Manual Boost fa StarTools 2 Cancel Reset Undo Mask Keep Help Before A ag e lt es rTools Illustration 43 Clicking on the yellow region of the spectrum with Filter Mode set to Reject attenuates that rgeion while keeping all other parts of the spectrum intact o Halo Killer attenuates the selected spectral line but only modifies pixels if it will be lighter or equal to its local neighbourhood while keeping stars intact This property when applied locally using a star Mask makes it especially suitable for eliminating halos around st
5. 14 StarTools 1 0 User Manual Interface i sn Illustration 3 Level setter control Setting the value represented in a level setter control is accomplished by clicking on the and buttons to increment or decrement the value respectively Alternatively you can click anywhere in the area between the and button to set a value quickly Illustration 4 Item selector control Switching items in the item selector is accomplished by clicking the arrows at either end of the item description Note that the arrows may disappear as the first or last item in a set of items is reached 15 StarTools 1 0 User Manual Modules Modules StarTools consists out of a number of integrated modules that perform different processing functions Roughly there are three types of modules e Modules that perform real time processing in the background while the user is free to tweak the parameters e Modules that perform non real time processing where the user initiates the rendering once the desired parameters are set These modules often require intensive calculations and will display a progress bar until the new result is available e Hybrid modules where some parameters are rendered real time and others only come into effect once the user initiates rendering during which a progress bar is shown until the new result is available All modules typically have a Cancel button which returns to the main screen ignoring
6. A virtual model of a 8 f 6 Newtonian design telescope left and its corresponding Point Spread Function right e Sample Size controls the fidelity of the model Larger values will approximate 47 StarTools 1 0 User Manual Synth energy distribution better and for larger areas but will take longer to compute and render In reality a star s starlight is scattered throughout the image and even beyond however these quantities of light are typically very minimal beyond a certain radius the exception being the light of very long diffraction spikes To speed up rendering therefore we can usually get away with calculating the light scattering over a much smaller area Sample Size around the star where it is actually noticeable In the case of very bright stars the area that the scattering is calculated for as specified by the Sample Size parameter may not be sufficient to accommodate most of the starlight If the latter is the case a clear boundary artefact will become visible where Synth stoppped calculating scattered light This boundary will often manifest itself faint squares around brighter star e Vanes specifies the number of spider vanes that hold the Central Obstruction for example the secondary mirror on a Newtonian in place This parameter is responsible for the appearance of distinct diffraction spikes The physical modelling dictates that o 1 vane will cause 2 fainter diffraction spikes o 2 equally spac
7. Clip sets any pixels that have a brightness of 10 or less to 10 This means that any pixel information that was darker than 10 will be lost 5 Add Headroom adds a base level of 5 of the maximum brightness to the image The image brightness is effectively squeezed into the remaining 95 no bottom end or top end clipping occurs 5 Clip sets any pixels that have a brightness of 5 or less to 5 This means that any pixel information that was darker than 5 will be lost e Normalize Filter specifies the amount of noise filtering that is performed before the image is normalised Increase this value if dead pixels are prevalent causing the natural background level to be much higher than black 0 Any image presented to the Levels module is automatically normalised That is the Levels module automatically determines the maximum and minimum pixel values that are present in the image Using these values the Levels module re allocates the dynamic range more effectively Note that dead pixels may cause the minimum pixel value detection to fail as these may cause the detection of false minimum values Use the Normalize filter if this situation arises The normalisation of the image will cause any background skyglow to vanish Sometimes skyglow is desirable from an aesthetic point of view Therefore the Levels module provides an option to add in a level of skyglow 41 StarTools 1 0 User Manual Lens Lens
8. Decreasing this value may yield more detail in smaller areas that are over or underexposed compared to their surroundings An example of the latter would be the details in stained glass when bright light shines through it in an otherwise dark church Gamma 1 and Gamma 2 specify the upper or lower boundary gamma values between which the exposures are generated The amount of exposures that are generated between the two boundaries are controlled by the Intervals parameter see above 62 StarTools 1 0 User Manual HDR e Saturation Preservation specifies how much colour information should be retained by a brightened pixel Lower this value if colour noise starts to become prevalent in brightened parts Lowering this value will counter colour noise by slowly draining colour from the pixel as it gets brighter Clicking the Do button will initiate rendering after which the user is presented with the result If you wish to only tame bright parts of your image simply set one of the Gamma parameters to 1 0 and the other to a value lower than 1 0 Conversely if you only wish to brighten parts of your image again set one of the Gamma parameters 1 0 and the other to a value higher than 1 0 Note that by setting the Noise Suppression parameter to On the HDR module assumes you wish to suppress any further high frequency detail from forming it assumes any additional high frequency detail that is found is noise However if your
9. 51 StarTools 1 0 User Manual Synth modes are available O Hybrid Remove Stars applies a proprietary compositing algorithm which is a hybrid between addition lightening and screening pixel math Any stars that are replaced are completely removed from the original before layering of the new ones is performed Lighten Remove Stars applies Lighten Only pixel math to composite the new image Any stars that are replaced are completely removed from the original before layering of the new ones is performed Addition Remove Stars adds the synthesised layer to the original however any stars that are replaced are completely removed from the original before layering of the new ones is performed Hybrid Keep Stars applies a proprietary compositing algorithm which is a hybrid between addition lightening and screening pixel math The original image including any stars that are to be replaced is kept and the synthesised layer is simply layered on top of it Lighten Keep Stars applies Lighten Only pixel math to composite the new image The original image including any stars that are to be replaced is kept and the synthesised layer is simply layered on top of it Addition Keep Stars adds the synthesised layer to the original The original image including any stars that are to be replaced is kept and the synthesised layer is simply layered on top of it Subtract Keep Stars is an experim
10. Add Headroom increases the brightness of all pixels in the image in such a way that pixels that would have been negative blacker than black are now at most O black This option effectively allocates headroom for the pixels that would otherwise be negative squeezing the rest of the pixels into a smaller dynamic range Note that no top end clipping will occur this way o Reduce modifies the modelled gradient in such a way that subtracting it from the original image will not result in any value less than 0 This effectively reduces the effectiveness of applying Wipe in order to keep the image from containing blacker than black pixels Cap green specifies whether Wipe should filter out any green hues from the image treating them as aberrations and noise The reasoning is that very few if any objects in outer space emit dominant green light Radius effectively specifies the strength or aggressiveness of the light removal process Lower values are more aggressive Radius controls how sensitive Wipe should be to sudden local changes in the unwanted light Use lower aggressive values for very localised gradients such as amp glow Use large values if a gradient occurs over large areas Corner Radius effectively specifies the strength or aggressiveness of the light removal process in the corners Lower values are more aggressive This setting is 23 StarTools 1 0 User Manual Wipe designed to allow Wipe to be mor
11. Illustration 25 show a 3x magnified before and after crop of the image of open cluster M11 as seen in Illustration 22 and Illustration 23 respectively We used the Point Spread Function PSF resulting from the virtual scope model of Illustration 21 54 StarTools 1 0 User Manual Synth First off it must be said that the original was of very good quality and did not stand much to gain from star resynthesis other than perhaps the addition of the diffraction spikes if so desired If the image however was of less quality for example suffering from bad focusing tracking issues or over processing artefacts etc then the resynthesis would have made a bigger difference in that the stars would now have been perfectly round in focus and natural looking The virtual scope model of Illustration 21 describes an 8 f 6 Newtonian design telescope having a secondary mirror holder which is mounted in the OTA by four spider vanes The four spider vanes have clearly caused 4 diffraction spikes at a 45 degree angle while the various other components have caused some subtle diffraction patterns and spokes emanating from the stars The concentration of stars in the middle has caused another diffraction effect a local brightening of the area around it This concentration of diffused starlight is regarded by some astrophotographers as desirable as it imparts a certain depth to the image This effect is most effective on globular clusters and wide f
12. Open Swap Clone Keep Help Illustration 51 Restoring the small detail around the stars that was destroyed by the Heal operation While the image of Illustration 50 is indeed very close to ideal upon very close inspection of the corrected stars it becomes apparent that some detail around the stars has been lost in a fuzz caused by the Heal module To correct this we once again launch the Layer module and Oper the original uncorrected image into the second layer Finally we set Mode to Luminance and any detail that was destroyed during the Heal operation will now have been restored 93 StarTools 1 0 User Manual Boost Illustration 52 Crop of Running Man Nebula magnified 3x before correction 94 StarTools 1 0 User Manual Boost Illustration 53 Crop of Running Man Nebula magnified 3x after correction 95 StarTools 1 0 User Manual Layer Layer Overview The Layer module allows the user to layer two separate layers on top of each other by means of pixel math Many additional algorithms and processing techniques may be accessed this way Usage Se StarTools 2 Mask Cancel Open Swap Clone Keep Help Illustration 54 The Layer module interface The Layer module interface consists out of the usual configuration of buttons on top and controls at the bottom end of the screen The Layer module shows three seperate images however 96 StarTools 1 0 User Manual Layer
13. Pixels that are not green in the mask e g pixels that are off will not be sampled by Wipe and will not influence the modelled gradients When masking out objects please make sure that every pixel of that object is masked out i e not green on When in doubt click the Shrink button in the Mask editor a few times to make sure only background pixels are tagged Please note that usage of a Mask in Wipe may impact processing times somewhat depending on how many pixels are masked out e g are not green in the mask This is normal behaviour To find out more about Masks and how to create them with ease please refer to the Masks chapter page 112 26 StarTools 1 0 User Manual Color Color Overview The Color module allows for flexible manipulation of an image s colour whether it be locally through the use of a mask or globally e le la StarTools A Co rTools 2 y one Reset Mask Cancel Keep Help Before A Illustration 11 Color module interface 27 StarTools 1 0 User Manual Color Usage The Color module has 9 adjustable parameters and settings Saturation specifies the amount of colour saturation as a percentage of the original image Increasing this value will make colours more vivid Decreasing this value will make colours less vivid until the image becomes a grayscale image Mask Fuzz specifies the kernel radius of a Gaussian blur to be non destructively applied to the cu
14. Synth module interface with an image of M11 image acquisition by Jim Misti Once a star mask and a scope model have been created the parameters for star synthesis should be set up Star synthesis itself may now be initiated by clicking the Do button Star synthesis and rendering are controlled by 10 parameters Please note that some of these parameters will apply in real time whereas some will only take effect once the Do button is clicked The following parameters are available e Gamma Adjust specifies the gamma adjust that is applied to the synthesised star 50 StarTools 1 0 User Manual Synth layer This parameter is an excellent way to control the prevalence of any diffraction spikes and flares Once a star layer is available i e the Do button has been clicked this parameter updates in real time e Core Whiteness specifies how much a star s color in the image influences its the color of its synthesised counterpart in the synthesised star layer High values will tend to mostly white stars whereas low values will tend to very colourful stars however adherent to the colour spectrum of a glowing body This parameter does not update in real time and is only applied upon the next rendering iteration triggered by clicking the Do button e Blur emulates blur due to atmospheric seeing conditions It is highly recommended to try and match the appearance of the original image in order to make the synthetic star layer
15. blend in A synthetic layer that is too sharp will likely stand out too much and be easily detectable as artificial Once a star layer is available i e the Do button has been clicked this parameter updates in real time OTA Rotation effectively specifies the rotation of the Point Spread Function relative to the image Most noticeably it controls the angle at which any diffraction spikes occur This parameter does not update in real time and is only applied upon the next rendering iteration triggered by clicking the Do button e Grow Mask grows the active star mask by the specified amount of pixels This parameter is particularly useful in Overlay Modes that remove the stars for which new artificial ones are synthesised increasing this value may help removing any traces of the old stars that are being replaced This parameter does not update in real time and is only applied upon the next rendering iteration triggered by clicking the Do button e Image Diameter specifies the image dimensions in arc minutes Synth uses this value in conjunction with the virtual scope model s aperture and focal length to determine the appropriate light concentration for the image and scope modelled e Overlay Mode specifies how Synth should composite the new image from the original image and the synthesised star layer Once a star layer is available i e the Do button has been clicked this parameter updates in real time The following
16. may cause you to perform incorrect colour correction miss colour casts gradients noise and other artefacts Subsequent viewing of your image on a correctly calibrated screen or in print may make these defects painfully visible It is highly recommended to use the best screen to which you have access At the very least your screen should be connected digitally i e by DVI or HDMI cable A dual monitor setup is ideal as it allows you to evaluate your image on different screens Please note that most cheaper integrated laptop screens are usually not ideal as a primary screen for processing and a secondary screen is highly recommended StarTools 1 0 User Manual Processing with StarTools Processing with StarTools An address to beginners and advanced users If you are a beginner learn become a member of the many forums on the Internet read up on imaging and processing best practices and most of all have fun StarTools will go a long way in satisfying your processing needs especially if your equipment is relatively humble StarTools is also an excellent companion for those using Global Rent A Scope or LightBuckets remote telescope rental services If you are a more advanced user StarTools contains modules that rival or best some of the house hold names in astrophotography packages and plug ins In addition StarTools sports some novel modules and approaches not found anywhere else potentially giving you an edge Whether you re a begin
17. the edges of the star core the latter often being the natural color of the star The introduction of color information into the core now further enables you to colour the complete star in its natural colour by applying some increased Saturation to the core in the Color module Expand Core expands the whiteness of the star core to the outer regions making the star appear bigger and brighter but also more defined An example can be seen in Illustration 38 where the star from Illustration 36 has had its core expanded Note that the star may subsequently be shrunk as a whole to reduce the apparent size increase Tighten Debloom attempts to attenuate any glare or halo around a star An example can be seen in Illustration 37 where the star from Illustration 36 has had its glare reduced Iterations specifies the amount of iterations the algorithm should go through This parameter typically controls the effect that is selected by the Mode parameter Mask Grow temporarily and non destructively performs the specified amount of Grow operations on the mask Increase this value if artefacts such as clearly visible rings start to form 79 StarTools 1 0 User Manual Boost Boost Overview The Boost module offers an extremely powerful and intuitive way to manipulate detail in colour images It s a simple matter of clicking on a feature such as a gas knot or a a swirl to make it stand out and br
18. the sharpening of astrophotographical images It performs well as a generic sharpening tool Note that a the usage of a Mask is highly recommended to deselect stars Masking out stars will keep Unsharp Mask from causing the black ring effect Alternatively the De ring option may be used o ST Definition is a StarTools proprietary sharpening technique which was specifically developed for the sharpening of astrophotographical images It is particularly effective on DSOs and nebulosity digging out delicate details and faint wisps of gas see comparison between unsharpened Illustration 31 and sharpened Illustration 32 It works by highlighting thin edges and transitions o ST Hybrid is a StarTools proprietary sharpening technique which was specifically developed for the sharpening of astrophotographical images This algorithm is a hybrid of the ST Sharp and ST Definition combining both their sharpening into one very effective sharpening and definition enhancing tool o Unsharp Mask applies a traditional sharpening technique to the image Note that a the usage of a Mask is highly recommended to deselect stars Masking out stars will keep Unsharp Mask from causing the black ring effect Alternatively the De ring option may be used 69 StarTools 1 0 User Manual Sharp Illustration 34 2x magnified crop of M42 sharpened with the traditional Unsharp Mask algorithm Due to the tendency to produce black
19. worse this effect is This causes stars to appear to have a cometary coma hence the name The Lens module can also correct for coma by applying a reverse distortion to the image 42 StarTools 1 0 User Manual Lens Usage e M StarTools 1 Cancel Keep Help Before NX Illustration 20 Lens module interface The Lens module has 9 adjustable parameters and settings e Red radius specifies the curvature strength of the red channel e Blue radius specifies the curvature strength of the blue channel e Center X specifies the central X coordinate of the distortion e Center Y specifies the central Y coordinate of the distortion e Red shift X specifies the amount of fractional pixels to shift the red channel s 43 StarTools 1 0 User Manual Lens pixels in the horizontal direction e Red shift Y specifies the amount of fractional pixels to shift the red channel s pixels in the vertical direction e Blue shift X specifies the amount of fractional pixels to shift the blue channel s pixels in the horizontal direction e Blue shift Y specifies the amount of fractional pixels to shift the blue channel s pixels in the vertical direction e Auto crop toggles the auto cropping feature on or off Because a distorted image may curve bulge when it is corrected not all pixels in the final Square image may be populated Auto cropping will crop the image in such a way that all pixels are popu
20. 49 Using the Heal module to create a copy with the image with be problematic stars erased Once satisfied with the mask click the Keep button and launch the Heal module Once in the Heal module increase the Grow Mask parameter until the masked stars have been healed over and you can no longer see any purple colouring where the stars once were Any other faint halo or bubble like artefacts are of no concern at this point Your image should look similar to the one in Illustration 49 Click the Keep button once satisfied with the result 91 StarTools 1 0 User Manual Boost 2 Mask Cancel Open Swap Clone Keep Help Illustration 50 The Layer module with the healed image in the Ist layer and the previously created halo free image loaded into the 2nd layer Next launch the Layer module Make sure your mask is fully set e g all pixels a green and tagged for processing To do this click Mask then Clear then Invert All pixels should now be selected in your Mask Click Keep to keep the mask and return to the layer module Back in the Layer module Open the image we saved previously see page 87 in the second layer and set Mode to Lighten The Layer module will now composite a halo free image Your interface should look similar to that of Illustration 50 Click the Keep button to finalise the result 92 StarTools 1 0 User Manual Boost SO startoois ame Mask Cancel
21. Layer StarTools n Mask Cancel Open Swap Clone Keep Help i Illustration 65 Artefacts around the 2 stars in the middle of the far right image In some case the rounding procedure may have caused some artefacts in the form of sharp boundaries as can be seen around the two stars in the middle of the right image of Illustration 65 In this case the Mask Fuzz parameter comes to the rescue eliminating the artefacts completely as seen in Illustration 66 Note that these artefacts were also the reason we grew our initial star mask by a few pixels so we had some additional pixels to blend with 109 StarTools 1 0 User Manual Layer StarTools n Mask Cancel Open Swap Clone Keep Help i Illustration 66 The Mask Fuzz parameter has eliminated the artefacts around the middle two stars We should now have an image with perfectly round stars with any background objects still intact Please note that this procedure relies on the fact that stars are bright dots that are brighter than their surroundings It is therefore not possible to use this technique to enhance more complex objects However a technique that may potentially be useful for more complex cases is a technique called Deconvolution StarTools does not currently offer this algorithm 110 StarTools 1 0 User Manual Heal Heal Overview The Heal module removes unwanted pixels from an image and substitutes new ones b
22. Mask from Illustration 55 Next we open up the Layer module We have loaded the less exposed image into the 2 layer i e the middle image by clicking on the Open button The composed result in the right image as seen in is close to what we want however there is clearly a transition between the two images at the Mask s boundaries However by simply using the Mask Fuzz parameter we can make the two images transition smoothly as seen in Illustration 57 Note that it may be worth experimenting with the Mask Fuzz parameter and or Grow ing the Mask in the Mask Editor though in this particular example we did not need to 100 StarTools 1 0 User Manual Layer Sa StarTools ESA startoo s l Mask Cancel Open Swap Clone Keep Help CO u Illustration 57 The two different exposures of M42 in the Layer module with the Mask Fuzz parameter set We now have successfully made a composite of two differently exposed frames Example 2 Rounding elongated stars Elongated stars may have several causes If your stars get progressively elongated towards the edge this may be due to coma which may be corrected by using the Lens module see page 42 or inserting a physical field flattener coma corrector in your image train Sometimes however tracking issues may be the cause elongated stars and this will result in streaks pointing the same way In this case the Layer module offers a way to correct this wit
23. SO the closest This way the selection algorithm can ignore any features that have the color of the DSO this way we get as little false positives as possible since for this exercise we re only interested in the stars If the selection algorithm does not pick out the fainter stars you can lower the value for Filter Sensitivity This will increase its aggressiveness If you find that fatter stars aren t correctly detected you may do one of two things You could increase the Max Feature Size or lower the Threshold from 100 The latter will add anything to the selection that is brighter than the specified threshold again ignoring any colors set by Exclude Color Since nothing is brighter than 100 brightness this setting has no effect if it is kept at 100 Star cores of the fatter stars are typically all white this is why setting Threshold to something slightly lower than 100 should select these cores Once you with your settings you can start the detection process by clicking the Do button 121 StarTools 1 0 User Manual Masks dea StarTools E 2 Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help rx Illustration 73 The mask with only stars selected After a short time the Auto function will return you to the Mask editor screen with the resulting new selection set see Illustration 73 Here you can evaluate the result and touch up the mask if necessary Example 2 Nois
24. The left image view shows the 1 layer This layer is not modified by any of the parameters and anything else is layered on top of this layer The middle image view shows the 2 layer This is the layer that gets layered on top of the 1 layer by means of pixel math The 2 layer is the layer that is affected by the controls If the 2 layer is not set yet the text Image Empty is displayed The right image view shows the resulting composite If the 2 layer is not set yet the text Image Empty is displayed since there is nothing to composite with and thus a result is not available yet The Layer module is controlled by 7 parameters Blend Amount specifies how much the final result and the original image should be blended This allows you to smoothly fade between processed layered and unprocessed versions of the image Cap Mode selects the way values below O and above unity full brightness are handled Clip simply cuts off any value lower than O or higher than unity full brightness and truncates them to 0 and unity respectively o Normalize recalibrates the dynamic range so that all values fit between O and unity This may mean that some pixels may be darkened to accommodate brighter parts Mode selects the pixel math operator to be used when layering the images o Normal simply copies the 2 layer over the 1 o Lighten copies only those pixels from the 2 layer that are lighter than tho
25. ars e Filter Width specifies how precise a spectral line is targeted Lower values ensure surrounding spectral lines are not affected while higher values ensure neighbouring spectral lines are affected as well Very narrow e g low values may cause very noticeable transitions between boosted and non boosted parts of an image Sampling Method specifies the method that is used to sample the image when the user clicks on it o 3x3 Average calculates the spectral line from a 3x3 pixel patch with the middle of the patch being the exact pixel that was clicked o Single Pixel calculates the spectral line from the exact pixel that was clicked e Mask Fuzz specifies the kernel radius of a Gaussian blur to be non destructively applied to the current mask This allows selections to be affected smoothly with no clear boundaries visible between processed and non processed pixels 83 StarTools 1 0 User Manual Boost In addition to the usual Cancel Keep and Help buttons Two more buttons are available in the Boost module e Reset completely resets the image to its original state and any modifications are undone e Undo undoes the last modification made to the image 84 StarTools 1 0 User Manual Boost Example Removing blue and violet halos due to chromatic aberration The Boost module can be very instrumental in removing halos due to axial also known as longitudinal chromatic aberra
26. ased on neighbouring pixels The Heal module is particularly useful for removing stars from an image or defects such as scratches dead pixels hot pixels etc Please note that the Heal module is not particularly useful for removing noisy pixels as tagged by the Auto feature Usage The Heal module is simple in its operation and only takes 3 parameters e Grow Mask specifies an additional amount of pixels the currently active mask should grow by The growing is applied temporarily and does not affect the active mask This parameter is useful when the active mask does not completely cover all pixels that require removal for example when you are trying to remove stars from an image and star halos remain e Algorithm switches between two algorithms o Gradient fills any patches of pixels that are marked for removal with a smooth gradient This algorithm is perfect for removing small amounts of pixels However since the substituted pixels are void of detail this algorithm may not be appropriate for large areas o Inpainting attempts to fill any patches of pixels that are marked for removal with detail based on neighbouring pixels e Second Pass specifies whether heal should perform a second pass after checking for pixels which were generated healed lighter than in the original In the case a pixel was generated which was lighter than the original the original pixel is used instead of the generated pixel This st
27. ate the green channel in this instance LRGB also imports colour images and extracts channels as appropriate For example importing a colour image into the red channel will automatically only extract the red data from the colour image Additionally LRGB features two types of chromatic colour noise reduction as well as a convenient ratio adjust in order to synchronise exposure times between channels Please note that when importing files all files must have the same dimensions There is one exception red green or blue channels may be exactly Y the size of the luminance channel This is so that the luminance channel can be recorded at 1x1 hardware binning while red green and blue may be recorded at 2x2 hardware binning In this case the red green and blue files will be automatically scaled up to match the size of the luminance channel 34 StarTools 1 0 User Manual LRGB sr PM StarTools Lum Red Green Blue Cancel Keep Help Illustration 14 LRGB module interface The LRGB module has 10 adjustable parameters and settings RGB Blur specifies the kernel radius of a Gaussian blur that is applied to the red green and blue channel in case of importing an LRGB image Note that this option only takes effect if a luminance channel is present Often more imaging time is spent on acquiring the luminance frame to which the human eye is much more sensitive The red green and blue data can often be of a much lower qual
28. ately tagged and your stars are small for example in wide field images you may reduce this value to reduce false positives Filter Sensitivity specifies how sensitive the selection algorithms should be to local brightness variations A lower value signifies a more aggressive setting leading to more features and pixels being tagged Threshold specifies a percentage of full brightness i e pure white below or above which a selection algorithm should detect features 119 StarTools 1 0 User Manual Masks Example 1 Star Detection The following example demonstrates how the Auto feature can be used for automated star detection We open up an image of a star field and go into the Mask editor as can be seen in Illustration 71 Note that we cleared the mask in this illustration for clarity but clearing the mask is not a necessary step Wanra Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help Illustration 71 An image of a star field From here we click the Auto button after which a screen will appear similar to that of Illustration 72 120 StarTools 1 0 User Manual Masks E A Cancel Do Help Illustration 72 The Auto feature screen In the Auto feature screen we adjust the parameters as reflected in Illustration 72 If you have a Deep Space Object DSO such as a nebula present in your image you may want to select an Exclude Color that matches the color of the D
29. aussian blur and Mask Fuzz applied It is only after we apply a Gaussian Blur and some Mask Fuzz that we can see a marked improvement in the right image see Illustration 79 noise has been reduced significantly but detail has not suffered 127 StarTools 1 0 User Manual Masks Example 3 Hot Pixel Removal The following example demonstrates how the Auto feature can be used to remove hot pixels Starlools 2 Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help Illustration 80 M31 in the Mask editor We open up an image of M31 which has quite a few hot pixels some red dots as well as some green and blue dots are clearly visible in Illustration 80 We then go into the Mask editor Note that we cleared the mask in Illustration 80 for clarity but clearing the mask is not a necessary step 128 StarTools 1 0 User Manual Masks StarTools StarTools Gani Illustration 81 Setting up the Auto function for hot pixel removal We then proceed to setting up the parameters for hot pixel removal We select Hot Pixels gt Threshold as our Selection Mode as well as the most aggressive values possible for hot pixel removal e We set Threshold to 0 meaning we don t care how bright a hot pixel must be before we remove it just remove anything we encounter e We set Filter Sensitivity to 0 meaning we want to identify as many features as possible for subsequent analysis no matte
30. barrier for urban beginners interested in imaging the skies A multi platform approach combined with not for profit pricing promotes the author s ideal of astrophotography for all We hope you enjoy the software and that it will be instrumental in getting the most from the equipment you have Clear skies Ivo Jager StarTools author StarTools 1 0 User Manual Getting Started and system requirements Getting Started and system requirements StarTools as with every other image processing suite is memory and CPU intensive A fast dual core processor with SSE3 is recommended as a minimum A 64 bit Operating System is highly recommended although 32 bit binaries are also available 3Gb of memory or more is highly recommended for 32 bit Operating Systems while 6Gb or more is recommended for 64 bit Operating Systems Please note that the MacOSX version of StarTools will not run on PowerPC processors StarTools will run on Netbooks with Intel Atom processors however limited CPU power and memory constraints will severely limit the size of the images that can be effectively processed The 32 bit version of StarTools will use a standard quality 32 bit signal path whereas any 64 bit version of StarTools uses a high performance high quality 64 bit engine Therefore if your hardware and operating system allows please choose to run a 64 bit executable for your platform as it contains some very important improvements over the 32 bit vers
31. cated that need to be resynthesised 2 Avirtual telescope model and its resulting energy distribution signature also Known as a Point Spread Function or PSF If you do not provide Synth with a star mask and a PSF Synth will display an message asking you to create them Synth does not work without them 45 StarTools 1 0 User Manual Synth Star Mask The creation of a star mask can be accomplished in seconds using the Auto function in the Mask editor see the Mask chapter page 112 and how to quickly create a star mask page 120 The Mask editor may be accessed through the Mask button in the Synth module or from the main screen Please note that while you re free to use Synth selectively on stars the most natural looking results are achieved when all stars are treated equally by Synth hence it is strongly recommended to simply use the Auto function in the Mask editor and select all stars While inspecting the Mask make sure that only stars are selected and not other bright objects which Synth erroneously may treat like stars deselect unwanted objects in the Mask editor Telescope modelling Besides a star mask a virtual scope model is created in the scope modeller as a second prerequisite Clicking the PSF button in the Synth module will launch the scope modeller The default settings will result in a model that should look similar to the one in Illustration 21 To the left we can see a top down v
32. d while some new stars have appeared The HDR module has successfully manipulated the local dynamic range to bring out new detail 60 StarTools 1 0 User Manual HDR Usage The HDR module is controlled by 6 parameters e Noise Suppression specifies whether the HDR module should attempt to keep the Signal to Noise Ratio SNR stable by applying a noise filter to any parts that are brightened The image in Illustration 28 shows a 3x magnified crop of the M42 image which has been rendered with Gamma 1 set to 3 0 and Noise Suppression set to Off The areas in the lower part of the image which have been lifted the most also clearly exhibit increased noise The image in Illustration 29 shows the same image processed with the same parameters except with Noise Suppression set to On The noise has been completely suppressed Illustration 28 3x magnified crop of M42 with Gamma I set at 3 0 and Noise Suppression set to Off 61 StarTools 1 0 User Manual HDR Illustration 29 3x magnified crop of M42 with Gamma I set at 3 0 and Noise Suppression set to On Intervals controls how many exposures are generated from the source image which are subsequently evaluated Boundary Blend controls the size of the area where transitions between the different exposures happen Increase this value if banding starts to occur or when the image looks particularly flat with details having an embossed look
33. data is of sufficient quality noise may not immediately form and true new high frequency detail may arise If you believe your data is of sufficiently high quality to withstand the brightening then keep Noise Suppression at the Off value 63 StarTools 1 0 User Manual Crop Crop Overview Ree A LE starToois Cancel Crop Help 514 pixels 718 Illustration 30 The Crop module interface The Crop module allows the user to crop the image This is particularly useful for framing a subject or to get rid of any stacking artefacts that are commonly found close to the edges 64 StarTools 1 0 User Manual Crop Usage The Crop module is fairly basic module with just 4 parameters e X1 specifies the first X coordinate e Y1 specifies the first Y coordinate e X2 specifies the second X coordinate e Y2 specifies the second Y coordinate The Crop module will show which parts of the image will be cut off by showing those pixels coloured in green Any pixels in the image that will be kept will be shown in their original pixels Clicking the Crop button will finalise the cropping and return the user to the main screen 65 StarTools 1 0 User Manual Sharp Sharp Overview The Sharp module offers some very flexible ways of sharpening an image Illustration 31 Crop of M42 image courtesy of Rowland Cheshire unsharpened Illustration 32 Crop of M42 sharpened with the Definition
34. e Reduction The following example demonstrates how the Auto feature can be used for Noise reduction Please note that is is just one of several ways of reducing noise in StarTools To find out about other types of noise reduction in StarTools please see the Levels and Color module chapters on page 37 and 27 respectively We open up an image of the Keyhole Nebula and go into the Mask editor as can be seen in Illustration 74 Note that we cleared the mask in this illustration for clarity clearing the mask is not a necessary step 122 StarTools 1 0 User Manual Masks SO startools zi Open Save Auto Illustration 74 An image of the Keyhole Nebula image courtesy of Rolf Wahl Olsen Co Tools 2 Sanos Cancel Do Help Illustration 75 The Auto feature screen Having clicked the Auto button we select Noise Coarse as out Selection Mode refer Illustration 75 Since the Noise Fine and Noise Coarse modes do not take head of any of 123 StarTools 1 0 User Manual Masks the other parameters there is nothing more to do here We can now click Do to commence the Mask generation 2 Illustration 76 The newly generated mask with noisy pixels tagged After a short amount of time the Auto function will return you to the Mask editor screen with the resulting new selection set see Illustration 76 As seen in Illustration 76 the selection algorithm has tagged noisy pixels
35. e Wipe module has 9 adjustable parameters and settings e Gradient Only specifies whether Wipe should only output the calculated model of the unwanted light o No Wipe subtracts the modelled gradient yielding the corrected image o Yes Wipe outputs the modelled gradient instead of the corrected image The resulting image contains all the unwanted light but NOT the corrected image or any of its features This mode may be useful to inspect the model that Wipe has calculated or to subtract the unwanted light at a later stage Note that subtracting this image by means of pixel math see the Layer module on page 96 will also dim any objects and stars that are present in the image 22 StarTools 1 0 User Manual Wipe o Yes Star Preservation is similar to Yes above with the exception that Wipe inserts gaps in the gradient model where Wipe has detected stars The resulting image can be safely subtracted from the original image by means of pixel math see the Layer module on page 96 to yield the corrected result with no dimming of the stars Mode specifies whether Wipe may adjust colour luminance brightness or both Clipping specifies what Wipe should do in the very worst case when Wipe needs to subtract light from a pixel that does not have enough light to subtract e g resulting in a blacker than black pixel o Clip lt 0 sets any negative values blacker than black pixels to O black o
36. e aggressive in the corners where vignetting may be a problem Vignetting is often characterised by a relatively sudden drop in light levels in the corners Therefore a more aggressive value for Corner Radius e g a lower value for Corner Radius than Radius may be in order Even a value of 0 may be appropriate Drop off point specifies how far from the centre of the image the radius should modulate to the Corner Radius value e g at which distance from the centre of the image will the Corner Radius take over from the Radius value This setting tells Wipe at which distance from the centre to expect vignetting to occur towards the corners Hence keeping the Drop off point value at the default 100 will tell Wipe not to expect any vignetting at all In that case Corner Radius will have no effect e Noise filter specifies the kernel radius of a Gaussian filter that temporarily removes high frequency detail such as noise and hot dead pixels from the image before passing it to the gradient modeller Use this setting if your image contains visible noise or hot or dead pixels to prevent Wipe from introducing artefacts such as those in the image in Illustration 10 A faint blueish gray lower right and yellowish centre patch can be seen The cause was a cluster of red and blue pixels respectively Note that employing the noise filter may result in some minor clipping in which case it will be dealt with in the manner specifi
37. e star s halo glare has been diminished 15 StarTools 1 0 User Manual Magic AC Giese Mask Cancel Keep Help Illustration 38 The Expand Core operator in effect Notice how the star has a more defined edge and the core is perfectly white 76 StarTools 1 0 User Manual Magic AC Giese Mask Cancel Keep Help Illustration 39 The Shrink Core operator in effect Notice how the star s core is no longer perfectly white but instead has inherited the faint colouring of the outer rim of the star often corresponding to the star s real colour 17 StarTools 1 0 User Manual AC Giese Mask Cancel Keep Help Illustration 40 The Shrink operator in effect Notice how the star has shrunk dramatically 78 StarTools 1 0 User Manual Magic Usage The Magic module itself is fairly simple to operate with the following 3 parameters Mode specifies what Magic should do with the star There are 4 different algorithms to chose from O Shrink quite simply shrinks the star An example can be seen in Illustration 40 where the star from Illustration 36 has been shrunk Note that further processing such as sharpening may be appropriate Shrink Core bleeds the edge color into the star s core effectively colouring the core with the rim s colors An example can be seen in Illustration 39 where the star from Illustration 36 has been subtly coloured according to the color at
38. ed by the Clipping parameter see above 24 StarTools 1 0 User Manual Wipe T A E O K 1 Open Save Undo Mask About Boost Layer MirrH Heal E ol MirrV Rotate Illustration 10 Two artefacts introduced by Wipe a result of 2 patches of hot pixels e Sampling size specifies the precision with which the gradient model is constructed Consider lowering this if using higher Radius values and computation takes too long Wipe comes with 3 handy preset buttons that quickly call up settings that are appropriate 25 StarTools 1 0 User Manual Wipe for common situations These buttons are Gradnt for the removal of gradients Vign for the removal of gradients and vignetting and Cast for the removal of general color casts While Wipe performs quite well on most images with minimal user intervention sometimes it needs direction on which parts of the image contain unwanted light and which parts of the image do not constitute unwanted light such as for example galaxies nebulas or in the case where trees and other terrestrial objects make up part of the scenery For those cases it may be appropriate to create a Mask in the mask editor which specifies which pixels of the image Wipe should sample for unwanted light and which pixels of the image Wipe should ignore Green pixels e g the pixels that are on in the mask will be sampled in order to reconstruct the background levels and any gradients
39. ed vanes will cause 2 brighter diffraction spikes o 3 equally spaced vanes will cause 6 fainter diffraction spikes o 4 equally spaced vanes will cause 4 brighter diffraction spikes e Vane Width specifies the width of the individual spider vanes Most noticeably this parameter influences the frequency with which the rainbow pattern in any diffraction spikes repeats itself e Vane Support Width specifies the width of any spider vane support mounted to the OTA as found in some scopes Most noticeably this setting has some subtle effects on the central flare in brighter stars e Backscatter specifies how much starlight is reflected by the primary mirror on to the various components in the OTA This light is subsequently emitted as diffused light having the effect of slightly reducing contrast and dulling down the brightness of any diffraction spikes and parts of any central flares 48 StarTools 1 0 User Manual Synth Central Obstruction specifies the size of a circular central obstruction typically a mirror holder as a percentage of the full aperture This settling greatly influences the diffraction pattern Note that a setting of 0 i e no obstruction effectively turns the virtual telescope into a refractor design Dispersion specifies the strength of the dispersion effect the subtle way in which different wavelengths colours of light are diffracted differently Most noticeably this setting controls the st
40. en finalising the image a base level commonly associated with natural phenomenon such as sky glow gegenschein etc may be added back to the image Note that the normalising algorithm may be confused by any non natural artefacts such as stacking artefacts and dead pixels 37 StarTools 1 0 User Manual Levels Usage E EER Cancel Keep Help Before s Illustration 15 Levels module interface The Levels module has 10 adjustable parameters and settings e Chroma Noise Reduction specifies the kernel radius of a Gaussian blur that is applied to the chrominance colour components of the image leaving the luminance brightness intact Often more imaging time is spent on acquiring the luminance frame to which the human eye is much more sensitive The red green and blue data can often be of a much lower quality and thus noisier without seeing much difference Blurring the red green and blue data effectively acts as a low pass filter eliminating the noise in the red green and blue channels Even with heavy blurring of the red green and blue channels the difference may be negligble however colour noise will be greatly reduced 38 StarTools 1 0 User Manual Levels Illustration 16 Running Man Nebula with Illustration 17 Running Man Nebula with severe chromatic noise Chroma Noise Reduction applied Red Luminance specifies the red channel s contribution to overall luminance Lowering this value may be benef
41. en pixels until it finds that All neighbouring pixels of a particular pixel are already filled green 113 StarTools 1 0 User Manual Masks O Or the pixel under evaluation is darker than the original pixel clicked Clicking on a green pixel will starting from the clicked pixel recursively turn off any green pixels until it can no longer find any green neighbouring pixels Flood Darker Pixels O Clicking a non green pixel will starting from the clicked pixel recursively fill the image with green pixels until it finds that All neighbouring pixels of a particular pixel are already filled green Or the pixel under evaluation is lighter than the original pixel clicked Clicking on a green pixel will starting from the clicked pixel recursively turn off any green pixels until it can no longer find any green neighbouring pixels Single Pixel O O Clicking a non green pixel will make a non green pixel turn green Clicking a green pixel will make green pixel turn non green 114 StarTools 1 0 User Manual Masks ooe JE e PA Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help Illustration 68 Clicking next to a feature note the position of the mouse cursor that is brighter than its surroundings will select it in a single click using the Flood Fill Lighter Pixels Brush Mode These different Brush Modes help in quickly selecting and de selecting features in the i
42. ental mode where synthesised stars are subtracted from the original This mode may help to bring out detail where fain detail is otherwise drowned out by a star s glare It is recommended to only use this mode with virtual refractor designs combined with some blur e Blend Original specifies what amount of the original image should make up the final image Once a star layer is available i e the Do button has been clicked this parameter updates in real time e Brightness Adjust specifies a corrective factor to the amount of light all stars 52 StarTools 1 0 User Manual Synth output Once a star layer is available i e the Do button has been clicked this parameter updates in real time e Core Noisiness specifies a percentage which is used to push the image beyond unity full white effectively overexposing the image somewhat This may aid Synth s star core detector to recognise noisy cores better Synth assumes big stars cores are white When they are not perfectly white for example due to noise or sharpening artefacts Synth s core detector may fail This parameter may help to overcome this issue This parameter does not update in real time and is only applied upon the next rendering iteration triggered by clicking the Do button After clicking the Do button and subsequent synthesis has been completed the screen image will update to reflect the newly synthesised layer similar to the screen in Illustratio
43. ep helps generating better fits for missing pixels in the case where stars are being removed 111 StarTools 1 0 User Manual Masks Masks What is a Mask The Mask feature is a integral part of StarTools Many modules use a mask to operate on specific pixels and parts of the image leaving other parts intact Besides operating only on certain parts of the image it allows the many modules in StarTools to perform much more sophisticated operations You may have noticed that when you launch a module that is able to apply a mask the pixels that are set in the mask will flash three times in green This is to remind you which parts of the image will be affected by the module and which are not If you just loaded an image all pixels in the whole image will be set in the mask so every pixel will be processed by default In this case when you launch a module that is able to apply a mask the whole image will flash in green three times Green coloured pixels in the mask are considered on That is to say they will be altered used by whatever processing is carried out by the module you chose Off pixels shown in their original colour will not be altered or used by the active module Again please note that by default all pixels in the whole image are marked on they will all appear green For example an on pixel green coloured in the Sharp module will be sharpened in the Wipe module it will be sampled for gradient modelling i
44. fective for reducing color noise in the darker areas o Filter progressively applies a filter to the darker areas as specified by the Noise Floor parameter greatly reducing any fine noise o Desaturate Filter combines the benefits of both Desaturate and Filter modes Digital Development is the main parameter to use when non linearly stretching a raw stacked image Closely related to the DDP Digital Development Processing algorithm invented by Dr Kunihiko Okano this parameter allows for quick Digital Development of a raw stacked image It effectively allots more headroom to the the very darkest and lightest parts of the image bringing out faint details and taming the brightest This behaviour is very similar to photographic film response to low and bright light Gamma adjust provides adjustment of the image to conform to the non linear response of media like your monitor printer etc which typically needs a gamma correction of 2 2 e Skyglow specifies the amount of skyglow to be added to the image Skyglow is effectively a minimum base level of brightness that all pixels will be set to Possible 40 StarTools 1 0 User Manual Levels modes are O Off no skyglow is added 10 Add Headroom adds a base level of 10 of the maximum brightness to the image The image brightness is effectively squeezed into the remaining 90 no bottom end or top end clipping occurs 10
45. ges Failure to take noise and or artefacts into consideration may lead to undesirable results and the introduction of further artefacts and or other unexpected visual aberrations In astronomical imaging noise is the enemy and StarTools offers many ways of countering noise and prohibiting it from propagating by nipping it in the bud as early as possible What StarTools does and does not do StarTools is an astronomical image post processing tool it takes raw stacked and aligned data and helps the user attain the best achievable result with that data StarTools at present does not perform stacking and or aligning of images There are 11 StarTools 1 0 User Manual Processing with StarTools many excellent utilities available that do this some of them free of cost Notable free software packages include Registax Deep Sky Stacker DSS and AVIStack all run on Windows StarTools at present does not offer any capturing or camera control abilities For a low cost capturing solution for Windows and MacOSX that also performs basic stacking and basic image processing please have a look at StarkLabs excellent Nebulosity software package If you use a Canon DSLR on Windows BackyardEOS is another great capturing utility http www astronomie be registax http deepskystacker free fr english index html http www avistack de http www stark labs com nebulosity html IO Wn RA http backyardeos binaryriver
46. h a little help from the Mask editor 101 StarTools 1 0 User Manual Layer ee Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help Illustration 58 Keyhole Nebula with severe tracking issues We open up an image of the Keyhole Nebula which suffers from severe tracking issues We then go into the Mask editor Illustration 58 Note that we cleared the mask in Illustration 58 for clarity but clearing the mask is not a necessary step 102 StarTools 1 0 User Manual Layer ge StarTools Sta ic iS Cancel Do Help Illustration 59 Using the Auto feature to automatically select the stars We d like to keep the Nebula intact and only modify the stars so we use the Auto feature to automatically select the stars for us see also the example on page 120 as can be seen in Illustration 59 103 StarTools 1 0 User Manual Layer 490 StarTools E 2 Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help Illustration 60 Keyhole Nebula with the elongated stars automatically selected The Auto feature will return us to the Mask editor screen with the stars selected for us similar to Illustration 60 104 StarTools 1 0 User Manual 490 StarTools 2 E Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help a y Illustration 61 The result of clicking the Grow button a few times However for star rounding purposes
47. hat Contrast should do in the very worst case when Contrast needs to subtract light from a pixel that s got not enough light to subtract e g resulting in a blacker than black pixel e Radius Minima specifies the strength or aggressiveness of the contrast enhancement process when dealing with areas that are too bright Lower values more aggressively suppress light areas e Radius Maxima specifies the strength or aggressiveness of the contrast enhancement process when dealing with areas that are too dark Lower values more aggressively lift dark areas e Noise filter specifies the kernel radius of a Gaussian filter that temporarily removes 31 StarTools 1 0 User Manual Contrast high frequency detail such as noise and hot dead pixels from the image before passing it to the contrast map modeller Use this setting if your image contains visible noise or hot or dead pixels to prevent Contrast from introducing artefacts Note that employing the noise filter may result in some minor clipping this is dealt with in the manner specified by the Clipping parameter see above Sampling size specifies precision with which the contrast map is constructed Consider lowering this if using higher Radius values and computation takes too long Se M StarTools 1 Back Keep Help Before Y Illustration 13 Contrast module 2 screen interface The Contrast module 2 screen has 2 adjus
48. he second layer The image must have the same dimensions as the 1 layer e Swap swaps around the 1 and 2 layer 98 StarTools 1 0 User Manual Layer Example 1 Integrating frames of different exposure lengths In this example we will demonstrate how to use the Layer module to integrate two frames that were recorded at different exposure lengths oa StarTools sr gt StarTools Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help Illustration 55 M42 with overexposed core selected as the Mask Image courtesy of Rowland Cheshire We first start off with the longest exposed image In Illustration 55 we have opened the Mask editor cleared the old Mask set the Brush Mode to Flood Fill Lighter Pixels and clicked just outside the overexposed core of M42 This has now selected the core An alternative way of selecting the overexposed parts would have been to activate the Auto feature setting the Selection Mode to Higlights gt Threshold making sure that Exclude Color is set to None and setting the Threshold to a value just under 100 This will select the very brightest white parts of the image possibly also including very bright stars 99 StarTools 1 0 User Manual Layer la starTools ry 2 Usa rTools Mask Cancel Open Swap Clone Keep Help Illustration 56 The two different exposures of M42 in the Layer module composed according to the
49. his should make light features marginally brighter and dark features marginally darker Dead Pixels lt Threshold selects dark high frequency components in an image such star edges halos introduced by overshapering nebula edges and dead pixels up to a certain size see Max Feature Size below and depending on a certain sensitivity see Filter Sensitivity below and whose brightness is darker than a certain percentage of the maximum value see the Threshold parameter below It then further narrows down the selection by looking at which pixels are likely the result of CCD defects dead pixels Hot Pixels gt Threshold selects high frequency components in an image up to a certain size see Max Feature Size below and depending on a certain sensitivity see Filter Sensitivity below It then further narrows down the selection by looking at which pixels are likely the result of CCD defects or cosmic rays also Known as hot pixels The Threshold parameter controls how bright hot pixels need to be before they are potentially tagged as hot Note that a Threshold of less than 100 118 StarTools 1 0 User Manual Masks needs to be specified for this mode to have any effect Noise Fine selects all pixels that are likely affected by significant amounts of noise Please note that other parameters such as the Threshold Max Feature Size Filter Sensitivity and Exclude Color have no effect in this
50. ial images in that most things in the image are extremely bright stars or extremely faint nebulas galaxies etc with little in between The Levels module is the first port of call in StarTools to fix this The Levels module was designed to do two things e Developing the raw linear CCD data into human eye friendly non linear data while minimising noise in parallel e Adjusting levels during post processing The Levels module is equipped with various ways to reduce noise The philosophy is that noise especially read noise is best dealt with early on while it is still linear Once noise gets stretched along with the real signal it starts to become harder to control and various algorithms may yield less optimal results because of its presence When developing a freshly stacked raw image please be sure to crop any stacking artefacts from the image It is also advisable to remove any dead pixels see the Masks and Heal chapters before proceeding The Levels module automatically normalises the image levels to maximise headroom for processing that is it stretches the brightness levels automatically so that the image uses the full dynamic range It is recommended to keep the levels normalised throughout processing in StarTools right up until finalising the image The reason for this is twofold 1 it is easier to spot features noise and or artefacts and 2 various algorithms in StarTools work best with normalised data Wh
51. icial when the luminance data from the red channel is of poor quality For example when imaging with an OSC or webcam without an infrared filter Illustration 18 Raw Jupiter Illustration 19 Raw Jupiter detail with all channels detail with only the green contributing to luminance channel contributing to equally luminance e Green Luminance specifies the green channel s contribution to overall luminance Lowering this value may be beneficial when the luminance data from the green channel is of poor quality Conversely increasing this value may benefit the image if the green channel is the most reliable of the channels 39 StarTools 1 0 User Manual Levels e Blue Luminance specifies the green channel s contribution to overall luminance Lowering this value may be beneficial when the luminance data from the blue channel is of poor quality For example when imaging with an OSC or webcam without a UV filter e Noise Floor specifies the brightness level below which the Deep Space noise reduction kicks in e Deep Space Noise Reduction switches between different modes of Deep Space Noise Reduction Deep Space Noise Reduction applies the chosen noise filter type to pixels that are darker than the Noise Floor see above Possible modes are o Off no noise reduction is performed o Desaturate progressively fades pixels to black amp white as specified by the Noise Floor parameter This mode is very ef
52. ield shots where star concentrations tend to correlate with nebulosity While there are other techniques to approximate this effect again this is a physically correct implementation and not an approximation We can observe that the different star colours are correctly reflected in the repetition of the rainbow pattern wavelengths colours that are less prevalent in the starlight are correctly attenuated Lastly one thing that Synth did clearly enhance over the original is the resynthesis and highlighting of the star cores of the smaller stars which had been reduced to indiscriminate blobs without a clear core 99 StarTools 1 0 User Manual Synth Illustration 25 Crop of synthesised image at 3x magnification 56 StarTools 1 0 User Manual Synth The ethics of using synthesised components in your image The desirability of deliberately introducing diffraction artefacts such as diffraction spikes and localised diffused starlight is up for debate and is down to personal preference However fact is that any diffraction artefacts that the user can introduce by Synth are physically correct and not an approximation Regardless the Synth module reconstructs starlight based on photometry performed on the original image measuring stars magnitudes color temperature and location It is up to the user to specify constraints and to decide what and how much is removed and what and how much is added back in its stead Astroph
53. iew of our virtual telescope You will notice it is very similar to what you would see if you were to look straight down a Newtonian Optical Tube Assembly OTA The right image represents the photon distribution of a point light e g a star as it is diffracted by the different components in the OTA Note that this image is not necessarily a representation of a star rather it serves as an indication of what individual stars will look like and how different OTA configurations influence the diffraction pattern as you design your virtual scope The virtual telescope model is controlled by 15 parameters e Aperture specifies the diameter of the OTA All other measurements and sizes controlled by the other parameters are relative to this parameter Together with the 46 StarTools 1 0 User Manual Synth Focal Length parameter and the Image Diameter in the Synth module aperture significantly influences the concentration of starlight of individual stars in the final image e Focal Length specifies the length of the OTA Together with the Aperture parameter and the Image Diameter in the Synth module this parameter influences the concentration of starlight of individual stars in the final image To calculate the focal ratio divide this number by the aperture e g for an aperture of 200mm and a focal length of 1200mm this yields 1200 200 f 6 eee Cancel Do 2 oy ON NY ON Illustration 21
54. ing out more detail in comparable parts of the image Boost works by isolating all elements from a particular colour spectrum and modifying only those elements Boost works particularly well on astronomical objects such as DSOs since a lot of these objects often have distinct colouring due to their chemical composition and corresponding emission lines 80 StarTools 1 0 User Manual Boost Usage The Boost module s behaviour is controlled by the following 4 parameters Filter Mode specifies the prime filter operation to be performed on the selected spectral line o Conservative Nudge enhances the selected spectral line but only if it can be accomplished without overexposing any parts of the image which effectively would have meant unrecoverable data loss The nudge operator is very useful for bringing out faint details that correspond to a spectral line o Nudge enhances the selected spectral line regardless of whether the operation overexposes any parts of the image Please note that overexposure e g clipping results in data loss The nudge operator is very useful for bringing out faint details that correspond to a spectral line StarTools 2 Cancel Reset Undo Mask Keep Help Before NS E gt D g StarTools Amon Illustration 41 Clicking on the darker purple region compare to the same region in Illustration 43 of the spectrum with Filter Mode set to Nudge
55. ion The 64 bit executable also allows StarTools to use more than 3Gb of memory should your system have more available The disk space that is required for StarTools is very minimal StarTools requires less than 2 Megabytes of disk space which is less than a typical MP3 song Despite its small size StarTools is fully self contained and does not depend on any external libraries or frameworks and no further components need to be installed To install StarTools simply download the ZIP archive and extract it to a location of your choice If you purchased a license key simply put the license key file in the same location as the StarTools executable and resources file lf you do not have a license key the executable will revert to being a demo without save capabilities If you do have a license key but the program still reports itself as a demo version after you copied the key as outlined above please contact us through our website at http www startools org Please note that throughout this manual screenshots of the Linux version are shown however please be assured that StarTools on other platforms will appear virtually identical Lastly calibrating your screen is of the utmost importance Failure to do so may invalidate 1 StarTools for Linux should run on most distributions with X11 and GTK installed StarTools 1 0 User Manual Getting Started and system requirements your processing efforts incorrectly calibrated screens
56. ithmically pushing pixel values in that channel towards the top or bottom end The average red green and blue values of the entire image expressed as a fractional values ranging from O to 1 may also be found in the control area This information may be helpful fine tuning the colours in the image where a desired colour balance is known Clicking on any pixel in the image will tell Color to use this pixel s color as a white reference to calibrate the entire image to The Reset button resets all sliders and settings to their default value 29 StarTools 1 0 User Manual Contrast Contrast Overview The Contrast module performs local contrast enhancement It optimises contrast in both bright and dark areas The Contrast module s interface consists of two screens On the first screen the parameters are set that are used to model a contrast map On the second screen the strength of the contrast enhancement as well as the way the contrast map is applied may be controlled The result on the latter screen is calculated in real time whereas the contrast map is not calculated real time a status bar is displayed due to its potentially long and intensive calculations 30 StarTools 1 0 User Manual Contrast Usage Se PM StarTools 1 Cancel Do Help Illustration 12 Contrast module 1 screen interface The Contrast module 1 screen has 5 adjustable parameters and settings e Clipping specifies w
57. ity and thus noisier without seeing much difference Blurring the red green and blue data effectively acts as a low pass filter eliminating the noise in the red green and blue channels Even with heavy blurring of the red green and blue channels in an LRGB composite the difference may be negligible however colour noise will be all but eradicated See Illustration 16 and Illustration 17 on page 39 for an example of colour noise and the benefits of colour noise reduction Channel interpolation toggles the interpolation of missing channels on or off This feature is particularly useful when for example creating a composite from Ha and 35 StarTools 1 0 User Manual LRGB Hb data in the red and blue channels without a green channel LRGB will automatically generate the green channel in this instance This feature is not just limited to the green channel It will do the same for any other missing channel e Cap green specifies whether LRGB should block any green hues from forming in the image The reasoning is that very few if any objects in outer space emit dominant green light e Red Ratio adjusts a multiplier that should be applied to the red channel Note that top end clipping may occur as a result This value may be used to attain the exposure duration equivalent of the other channels For example if the red frame was a 30 minute exposure and the green and blue frames were both 45 minute exposures then the red ratio
58. l ways as it relates to several aspects of the new image versus the old image 8 E StarTools A 2 Cancel Keep Help ES startoo s Illustration 35 The Bin module interface As can be seen in Illustration 35 the value indicator in the level setter control reads scale noise reduction 50 00 400 2 00 bits This may be read in the following ways e The image s X and Y dimensions have been reduced to 50 of their respective original values e Noise has been reduced to 50 of its original level e The original image was 400 the size of the newly binned image e There has been an improvement of 400 to noise levels e Bit depth has been increased by 2 00 bits Notice how noise reduction does not increase linearly with image size reduction i e to get more noise reduction the image will have to be scaled down more and more 73 StarTools 1 0 User Manual Magic Magic Overview The Magic module gives the user control over the appearance of stars in the image during post processing Various operators are available E fee 2 Mask Cancel Keep Help Illustration 36 A test image with no further processing all parameters set to 0 The big white star has been selected as our subject by means of a mask 74 StarTools 1 0 User Manual Magic AC Giese Mask Cancel Keep Help Illustration 37 The Tighten Debloom operator in effect Notice how th
59. lar size This allows multi scale processing whereby different versions of the image with different scales may be processed independently and recomposed at a later stage Additionally selective sharpening is also supported by means of a Mask This way the unwanted sharpening of any features can be easily avoided 67 StarTools 1 0 User Manual Sharp Usage Mask Cancel Keep Help E AS gici a Illustration 33 The Sharp module interface The Sharp module is controlled by 8 parameters e Threshold controls the minimum brightness a pixel needs to have before sharpening kicks in This parameter is particularly useful to avoid sharpening and thus exacerbating any noise in darker areas e Mask Fuzz specifies the kernel radius of a Gaussian blur to be non destructively applied to the current mask This allows selective sharpening to be applied smoothly with no clear boundaries visible between patches of sharpened and non sharpened pixels e Scale 1 and Scale 2 specify an upper and lower boundary of a range of feature 68 StarTools 1 0 User Manual Sharp sizes that will be sharpened Any feature between the size of Scale 1 and Scale 2 will be sharpened while anything outside this range will be left as is e Algorithm specifies the sharpening algorithm that should be used There are 4 settings o ST Sharp is a StarTools proprietary sharpening technique which was specifically developed for
60. lated This will mean however that some pixels at the edges may be lost as a result To correct coma e g perform field flattening simply adjust the Red Radius and Blue Radius by the same amount until stars no longer appear elongated 44 StarTools 1 0 User Manual Synth Synth Overview The Synth module is one of the most complex but gratifying modules in StarTools Synth allows the user to augment or even completely replace starlight by modelling new starlight based on photometry information extracted from the image Essentially Synth reverses the full image train and models a new virtual one step by step The Synth module has several uses e Making stars brighter and tighter e Making stars look like they were imaged from orbit e Breathing life into flat images by re modelling physically correct starlight energy distribution e Modelling physically correct diffraction spikes e Modelling starlight as it would look through much bigger and more expensive telescopes or wholly different designs Synth performs best on images where it can perform accurate photometry that is images that are of sufficient resolution sharpness and with minimal noise Please note that Synth does not modify anything else but stars and starlight Prerequisites Before Synth can perform star synthesis the user will need to provide it with two crucial items 1 Astar mask outlining where in the original image stars are lo
61. ls that were on The Shrink button turns off all the green pixels that have a non green neighbour effectively shrinking any selected regions 11 Tip to quickly turn on all pixels click the Clear button then the Invert button 116 StarTools 1 0 User Manual Masks e The Grow button turns on any non green pixel that has a green neighbour effectively growing any selected regions The Undo button allows you to undo the last operation that was performed As with the different modules in StarTools the Keep and Cancel buttons work as expected Keep will keep the edited Mask and return while Cancel will revert to the Mask as it was before it was edited and return As mentioned before when launching the Mask Editor from a module pressing the Keep or Cancel buttons will return StarTools to the module you pressed the Mask button in The Auto Feature oC Gets Cancel Do Help gt Illustration 70 Mask s Auto feature interface The Auto function is a very powerful feature for quickly isolating features of interest stars noise hot or dead pixels etc For example isolating only the stars is in an image is a necessity for obtaining any useful results from the Magic module see page 74 For examples on how the Auto feature is used in conjunction with the different modules in StarTools please refer to the star detection noise reduction and hot pixel removal examples o
62. mage For example while in Flood Fill Lighter Pixels mode try clicking next to a bright star or feature to select it see Illustration 68 Click anywhere on a clump of on green pixels to toggle the whole clump off again Please note that depending on the size of the image the mode selected and the amount of pixels that need to be flood filled there may be a minor delay in response between clicking on the image and seeing a result This is normal behaviour 115 StarTools 1 0 User Manual Masks o rTools Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help Illustration 69 Pressing the Invert button on the mask in Illustration 68 Apart from the different brush modes various other functions exist to make editing and creating a Mask even easier The Save button allows you to save the current mask to a standard TIFF file The Open button allows you to import a Mask that was previously saved by using the Save button Note that the image that is being opened to become the new Mask needs to have the same dimensions as the image the Mask is intended for The Auto button is a very powerful feature that allows you to automatically isolate features For more details please see the sub chapter on the Auto feature on page 117 The Clear button turns off all green pixels i e it deselects all pixels in the image The Invert button turns on all pixels that are off and turns off all pixe
63. mode Noise Coarse selects all pixels that are likely affected by significant amounts of noise This algorithm is more aggressive in its noise detection and tagging than Noise Fine Please note that other parameters such as the Threshold Max Feature Size Filter Sensitivity and Exclude Color have no effect in this mode Sobel Edge selects all pixels that are likely to belong to the edge of a feature Use the Threshold parameter to set sensitivity where lower values make the edge detector more sensitive As has been alluded to above some of the selection algorithms are controlled by additional parameters Exclude Color tells the selection algorithms to not evaluate specific colour channels when looking for features This is particularly useful if you have a predominantly red purple and blue nebula with white stars in the foreground and say you d want to select only the stars By selecting Exclude Color Purple Red Blue you are able to tell the selection algorithms to leave features in the nebula alone since these features are most prominent in the red and blue channels This greatly reduces the amount of false positives Max Feature Size specifies the largest size of any feature the algorithm should expect If you find that stars are not correctly detected and only their outlines show up you may want to increase this value Conversely if you find that large features are being inappropri
64. n 23 Further tweaking and modification is now possible Again please be aware that some parameters only come into effect once the Do button is clicked and synthesis has been initiated If you notice any artefacts in the form of distinct squares of light around brighter stars then this is caused by a too low PSF sample size There are multiple ways of fixing this increasing the sample size adjusting the gamma lower or or increase the angular size value If starlight seems to be overconcentrated adjust gamma create a new virtual scope model with a different aperture and or focal length or increase the angular size value Always scrutinise the image looking for errors it is possible the Synth module did not correctly detect a star s size or did not correctly seperate multiple overlapping stars instead detecting them as a single large star Experimentation with the different blend modes may be in order for best results deepening on the source image It is acceptable for local contrast to suffer somewhat pushing up background levels This is easily remedied by using the Contrast module Subsequent sharpening of the synthetic stars may also benefit your image 53 StarTools 1 0 User Manual Synth CL 2 PM StarTools Mask PSF Cancel Do Keep Help Illustration 23 Synthesised image of M11 modelled with the 8 f 6 Newtonian PSF of Illustration 21 Examining an output sample Illustration 24 and
65. n Synth it will be scanned for being part of a star in Heal in will be removed and healed in Layer it will be layered on top of the background image etc To recap e Ifa pixel in mask is on coloured green then this pixel is fed to the module for processing e Ifa pixel in mask is off shown in original color then tell the module to keep the pixel as is hands off do not touch or consider 112 StarTools 1 0 User Manual Masks The Mask Editor 6 5 rTools Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help Illustration 67 The Mask Editor showing an image with all pixels selected for processing The Mask Editor is accessible from the main screen as well as from the different modules that are able to apply a mask The button to launch the Mask Editor is labelled Mask When launching the Mask Editor from a module pressing the Keep or Cancel buttons will return StarTools to the module you pressed the Mask button in As indicated by the Click on the image to edit mask message clicking on the image will allow you create or modify a Mask What happens when you click the image depends on the selected Brush Mode While some of the Brush Modes see below seem complex in their workings they are quite intuitive to use There are three Brush Modes e Flood Fill Lighter Pixels o Clicking a non green pixel will starting from the clicked pixel recursively fill the image with gre
66. n page 120 122 and 128 respectively 117 StarTools 1 0 User Manual Masks The type of features to be isolated are controlled by the Selection Mode parameter Light Features Highlight gt Threshold is a combination of two selection algorithms One is the simpler Highlight gt Threshold mode which selects any pixel whose brightness is brighter than a certain percentage of the maximum value see the Threshold parameter below The other selection algorithm is Light Features which selects high frequency components in an image such as stars gas knots and nebula edges up to a certain size see Max Feature Size below and depending on a certain sensitivity see Filter Sensitivity below This mode is particularly effective for selecting stars Note that if the Threshold parameter is kept at 100 this mode produces results that are identical to the Light Features mode Light Features selects high frequency components in an image such as stars gas knots and nebula edges up to a certain size see Max Feature Size below and depending on a certain sensitivity see Filter Sensitivity below Highlight gt Threshold selects any pixel whose brightness is brighter than a certain percentage of the maximum value see the Threshold parameter below If you find this mode does not select bright stars with white cores that well open the Levels module and set the Normalization a few pixels higher T
67. nd processing is being performed and the image will be updated shortly with the new settings taking effect 17 StarTools 1 0 User Manual Modules Detecting gradients Cancel 1 pixels 256 x 256 pixels Illustration 6 The Wipe module in the process of gradient modelling Some modules will not automatically perform real time processing in the background due to the CPU intensiveness of their algorithms These modules will have a Do button This button will initiate the processing once the user is satisfied with all parameters and settings A status bar such as the one in Illustration 6 will show progress Once the process completes the image will update with the user may evaluate the result Any subsequent tweaking requires the Do button to be clicked updating the the image 18 StarTools 1 0 User Manual Wipe Wipe Overview The Wipe module is one of the more powerful modules in StarTools Its main purpose is to eliminate unwanted light in an image This unwanted light may come in the form of gradients colour casts light pollution vignetting amp glow or even a combination of all five e Gradients are usually prevalent as gradual increases or decreases of background light levels from one corner of the image to another e Colour casts are a tint of a particular colour which contrary to a gradient affects the whole image evenly e Light pollution is the presence of a persistent haze of often c
68. nents in your MAC cooocococccooccconcconcconnnconccnoncconccnnncncnnnnos 57 A O a NNR 58 OVET VI EW iia 58 A aR a E KE E A EEE O E E E E E TON 6l COP A A A to E 64 OM ir E chee bersuup aes oxnssuashseaitziauea lateeunboes EEN 64 Me sacha fe A MIE US Nahr EA O EE 65 DN E ascent entice 66 O 66 O 68 A A 71 A ON 71 When should you consider software DINOINE oooooconocccocccoonaconccoononancconnnconocnnnononnonnn con non nccnccnnnss 71 Us tal 73 Mi A Aa OR 74 A O ER 74 Un act eer Sa en A Nasr a Gano gl ian erate ae cena a ase a 79 BOOS Fa ah A A ta a 80 Odo 80 A ae Eaa E E a komaautysany het ace quay ae a vane dudhondedthraud E a A Toa Ea aLa A 81 Example Removing blue and violet halos due to chromatic aberration ccccesceeseeseeeeereeeees 85 LAV A O E ITA 96 RPV A A A O hear aaa 96 UR o DoS 96 Example 1 Integrating frames of different exposure lengths cee eeceeceeseeeteeeeneeeeneeeesneeeeee 99 Example 2 Rounding elongated Stars A a wioureaness 101 A i ich crn E eee a elena sean aap eh ca shares a eae 111 Ss stsines srk ra tll ea a ad ass cia ania O 111 StarTools 1 0 User Manual A beseenmyounedosduan ugunehnabanehane cates czedamhaanddulpseunnwten bene sguyeateberoeaane 111 A A A 112 Mutis Mis a a Nah eee NUN tn eee coon eas 112 The MI los 113 O nari ope seen RRR Ta oS PE A A ee 117 Example 1 Star ete Cin o o O 120 Example 2 Noise REUS A Made Sears 122 Example Hot Pixel Removal da aa E 128 Acknowledgemen
69. ner or an advanced user don t be afraid to ask help on the StarTools forums at http www startools org forum For its modest size and goals StarTools is a complex beast Like any other complex piece of software there will be a learning curve involved though we ve sought to minimise this learning curve wherever we had the chance StarTools automates or abstracts a lot of tasks that may be quite tedious time consuming or prone to error in other processing suites Lastly regardless whether you re a beginner or advanced user don t be afraid to experiment More so try to learn why algorithms and techniques work the way they do and how they can be of benefit to your work It will make you that much more creative and agile when processing Understanding the strengths and weaknesses of your image train from photon to pixel will make it easier to choose the right algorithms and parameters to get the most out of your precious data As alluded to by the quote from accomplished astrophotographer Rogelio Bernal Andreo at the start of this manual There are as many schools of astroimage processing as there are astrophotographers astrophotographical image processing is more about interpretation of your data than presenting cold hard fact there is no absolute right way 2 http www global rent a scope com 3 http www lightbuckets com 10 StarTools 1 0 User Manual Processing with StarTools of processing an image and n
70. o one has a monopoly on asserting what constitutes a good image Of course that does not mean that best practices and techniques should be abandoned but these words of wisdom are something to keep in mind should doubt set in Making your data StarTools friendly There are some important things you should know about how modules work with pixel data in StarTools First of all many algorithms require a mask i e a second image which tells StarTools which pixels to operate on and which pixels are off limits to operate effectively As a matter of fact a number of modules will not yield any useful results without a mask set To find out more about masks see the Masks chapter page 112 Secondly the algorithms that StarTools employ are very sensitive to excessive noise artificial artefacts such as stacking artefacts borders text etc and hot and or dead pixels When processing images that contain such artefacts and noise please be aware of their existence and try to eliminate them whenever possible before starting your processing This may mean using the Crop tool to crop the image until stacking artefacts are no longer visible at the borders or using the Mask Heal and Layer modules to heal hot and or dead pixels and or noise see examples on page 128 and 122 Some modules come with an additional parameter that lets you specify a noisiness level of the image so that the module can take precautions when processing noisy ima
71. oloured light caused by urban street lighting e Vignetting manifests itself as the gradual darkening of the image towards the corners and may be caused by a number of things Amp glow is caused by circuitry heating up in close proximity to the CCD causing localised heightened thermal noise typically at the edges On some DSLRs and Compact Digital Cameras amp glow often manifests itself as a patch of purple fog near the edge of the image 19 StarTools 1 0 User Manual Wipe Illustration 7 M101 courtesy of Charles Kuehne The image in Illustration 7 suffers from three sources of unwanted light a gradient starting at the upper right corner light pollution in the form of the typical yellowish light emitted by typical urban sodium lamps and vignetting clearly seen in the darkening of the corners 20 StarTools 1 0 User Manual Wipe Illustration 8 M101 processed by StarTools Wipe Wipe works by calculating a model of the unwanted light and then subtracting it from the image The result is an image that is free from the unwanted light sources as can be seen in the image in Illustration 8 Wipe has eliminated the unwanted sources of light while keeping the actual subject intact 21 StarTools 1 0 User Manual Wipe Usage Esa StarTools PF PF 4 2 A Sha f PE StarToois Gradnt Vign Cast Mask Cancel Do Keep Help Before Y B Illustration 9 The Wipe interface Th
72. onvolution algorithm in which case the oversampled data is used to recover finer detail than is otherwise available in the original oversampled data 71 StarTools 1 0 User Manual Bin Finally you could also consider software binning as a last resort to reduce noise even if detail is removed In this case with reduced data binning may make the difference between a usable and an unusable data set by augmenting data at the expense of resolution Please note that some dedicated CCDs offer binning in hardware typically only a 2x2 mode Hardware binning will yield an even better signal to noise ratio as the hardware binning also reduces read out noise which software binning does not Depending on your subject and site conditions hardware binning may make the difference between a usable image and a noisy pixel soup In these conditions where read noise mitigation is of the utmost importance hardware binning will yield significantly better results than post acquisition software binning Depending on your CCD characteristics hardware binning may also have some drawbacks such as diminished well depth or complete loss of colour in case of a One Shot Colour OSC device Of course software binning is an optional post processing step whereas hardware binning is performed during capture and is irreversible 72 StarTools 1 0 User Manual Bin Usage The Bin module takes a single parameter Scale whose value can be read in severa
73. otographer and author Jerry Lodriguss wrote an interesting article on the ethics of astronomical image processing and image manipulation When you publish your image it is common practice to mention the equipment software and software plug ins that were used to produce your image You may find mentioning the use of the Synth module appropriate 9 http www astropix com HTML J_DIGIT ETHICS HTM 57 StarTools 1 0 User Manual HDR HDR Overview Elda StarTools ry LE starToois a Cancel Do Keep Help The HDR module optimises an image s dynamic range lts algorithm was designed to bring out faint detail that is hidden in under and over exposed parts of an image by locally increasing the dynamic range The algorithm works by intelligently evaluating the image at different exposures and picking the optimal brightness for each pixel 58 StarTools 1 0 User Manual HDR Illustration 26 M42 image before HDR treatment image courtesy of Rowland Cheshire Illustration 26 shows an image of M42 before HDR treatment 59 StarTools 1 0 User Manual HDR Illustration 27 M42 image after HDR treatment with the default parameters Illustration 27 shows the same image of Illustration 26 after HDR treatment with all parameters at their default values Notice how the brightness of the core has been toned down while new detail has become visible Also notice that stars that were already visible have not been affecte
74. r how faint This allows us to detect warm pixels These are pixels that are not completely defunct but still yield a higher value than they should Once you are satisfied with the parameters click the Do button to commence the Mask generation 129 StarTools 1 0 User Manual Masks en Startools A gt StarTools Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help Illustration 82 The mask with hot pixels after several clicks on the Grow button After a short time the Auto function will return you to the Mask editor screen with all hot pixels tagged However unless zoomed in the selection may be hard to see as hot pixels are typically one pixel in size While the hot pixels should have been detected successfully their ill effects may stretch beyond just a single pixel This is typically true for images that have been debayered such as images taken with an OSC DSLR compact camera or webcam It is therefore prudent to grow the selection by a couple of pixels To do this simply click on the Grow button a couple of times Your mask will now look similar to the one in Illustration 82 notice how the hot and warm pixels are now clearly visible as green dots All we have to do now is remove the aberrant pixels We do this using the Heal module see also page 111 130 StarTools 1 0 User Manual Masks A nia StarTools Mask Cancel Keep Help Illust
75. ration 83 The Heal module showing a healed hot pixel free version of M31 using the hot pixel mask Simply launching the Heal module will yield a result similar to that of Illustration 83 The hot and warm pixels will have disappeared Note that if we forgot to use the Grow button in the Mask editor we can use the Grow Mask slider to do it here on a temporary basis that is without modifying the active Mask 131 StarTools 1 0 User Manual Acknowledgements Acknowledgements StarTools and this manual were made possible by the contributions of the following people e Alan Mehan Australia e Charles Kuehne USA e Jim Misti USA e Marc Aragnou Australia e Pete Scully South Africa e Roger Groom Australia e Rolf Wahl Olsen New Zealand e Rowland Cheshire Australia e Warren Maag Australia The author whishes to thank them for providing images equipment and their valuable time beta testing StarTools 132
76. rength of the rainbow effect in the diffraction spikes Note that the physical modelling dictates that stars that do not emit all wavelengths equally will generate rainbows with different colours attenuated Screws specifies the number of screws that protrude from the OTA into the light path Clips specifies any mounting clips that keep the primary mirror or lens in place Clip size specifies the size of any mounting clips that keep the primary mirror or lens in place Focuser specifies the type of focuser that the OTA is equipped with The presence of a focuser subtly affects the central flare s diffraction pattern adding a faint but distinct spike The different options are o None no focuser protrudes from the OTA into the light path o 1 25 inch a standard 1 25 focuser extends into the OTA o 2 inch a standard 2 focuser extends into the OTA o 3inch a standard 3 focuser extends into the OTA Focus Travel specifies how much of the focuser protrudes into the OTA Focuser Angle specifies the angle at which the focuser is mounted to the OTA Once you are satisfied with the model click the Do button to commence the high resolution Point Spread Function calculation Upon completion of the calculation you will be returned to the Synth module 49 StarTools 1 0 User Manual Synth Star Synthesis Kso rTools Mask PSF Cancel Do Keep Help Illustration 22 The
77. rings around stars the use of an inverse star mask is highly recommended e Channels specifies whether the sharpening algorithm should process each colour channel independently or if it should only sharpen their combined luminance o Luminance makes pixels brighter or dimmer as determined by the sharpening algorithm but colour remains the same RGB applies sharpening to each colour channel separately impacting overall colour as well as brightness Strength specifies the strength of the sharpening effect Note that this value may be negative causing instead the suppression of details The latter is especially useful for performing multi scale processing where for example the user may wish to bring out faint large structures in lieu of a dominant busy star field in the foreground To blur instead of sharpen an image use a negative value for strength and set Channels to RGB 70 StarTools 1 0 User Manual Bin Bin Overview The Bin module offers the user a way to trade off resolution for a better signal to noise ratio SNR Far from being a simple scaler the Bin module offers arbitrary sized fractional binning of pixel data Similar software algorithms are found in the more recent consumer digital cameras often labelled low light mode allowing for very high ISO values to be achieved at the expense of resolution The StarTools Bin algorithm however still yields correct results at arbitrary
78. rrent mask This allows selections to be affected smoothly with no clear boundaries visible between processed and non processed pixels Red Gamma adjusts the gamma value of the red channel Green Gamma adjusts the gamma value of the green channel Blue Gamma adjusts the gamma value of the blue channel Red Ratio adjusts a multiplier that should be applied to the red channel Note that this value is automatically adjusted by clicking on the image to adjust white balance Green Ratio adjusts a multiplier that should be applied to the green channel Note that this value is automatically adjusted by clicking on the image to adjust white balance Blue Ratio adjusts a multiplier that should be applied to the blue channel Note that this value is automatically adjusted by clicking on the image to adjust white balance Cap green specifies whether Color should block any green hues from forming in the image The reasoning behind this feature is that very few objects in outer space emit predominantly green light The Color module attempts to keep luminance perceived brightness constant and works on the colour information only Changing a colour channel s ratio will increase that channel s prevalence in lieu of the others and vice versa Changing the ratio changes the colour channel s prevalence linearly 28 StarTools 1 0 User Manual Color Changing a color channel s gamma will change a channel s prevalence logar
79. s are found in the top right corner along with a zoom percentage indicator Panning controls scrollbar style are found below and to the right of the image as 13 StarTools 1 0 User Manual Interface appropriate depending on whether the image at its current zoom level fits in the application window mn A ES ta 7 9 StarTools PE StarToois Mask Cancel Keep Help Illustration 2 A typical module interface The image in Illustration 2 shows the layout of a typical module in this case the Magic module with the toolbar situated on top and the different parameters and settings specific to the module situated at the bottom Common to most modules is a Before After button situated next to the zoom controls which toggles between the original and processed version of an image for easy comparison All modules come with a Help button in the toolbar which explains in brief the purpose of the module Furthermore all settings and parameters come with their own individual Help buttons left to the parameter control These help buttons explain again in brief the nature of the parameter or setting The parameters in the different modules are typically controlled by one of two types of controls e A level setter which allows the user to quickly set the value of a parameter within a certain range An item selector which allows the user to switch between different modes
80. s com 12 StarTools 1 0 User Manual Interface Interface Navigation within StarTools generally takes place between the main screen and the different modules StarTools navigation was written to provide a fast predictable and consistent work flow There are no windows that overlap obscure or clutter the screen Where possible feedback and responsiveness will be immediate Many modules in StarTools offer on the spot background processing yielding quick final results for evaluation and further tweaking agg rta gt B O K 1 pe Open Save Undo Mask About P Wipe Color Cntrst LRGB a Levels Lens ATA ajo Synth HDR El Crop Sharp Boost Layer Illustration 1 The main screen interface M42 courtesy of Rowland Cheshire In both the main screen and the different modules a toolbar is found at the very top with buttons that perform functionality that is specific to the active module In case of the main screen this toolbar contains buttons for opening an image saving an image undoing redoing the last operation invoking the mask editor and opening an about dialog Exclusive to the main screen the buttons that activate the different modules reside on the left hand side of the main screen Note that the modules will only successfully activate once an image has been loaded with the exception of the LRGB module see page 34 Consistent throughout StarTools a set of zoom control button
81. se in the 1 layer o Darken copies only those pixels from the 2 layer that are darker than those in the 1 layer o Multiply multiplies the pixels from the 1 layer by the pixels from the 2 layer o Add adds the pixels from the 1 layer to the pixels from the 2 layer 97 StarTools 1 0 User Manual Layer o Subtract subtracts the pixels in the the 2 layer from the pixels in the 1 layer o Divide divides the pixels from the 1 layer byt the pixels from the 2 layer o Luminance applies the luminance brightness from the 2 layer to the 1 layer keeping any colour information intact o Chroma applies the chroma colour information from the 2 layer to the 1 layer e Gaussian Blur applies an optional Gaussian filter to the second layer e Mask Fuzz specifies the kernel radius of a Gaussian blur to be non destructively applied to the current mask This allows selections to be affected smoothly with no clear boundaries visible between processed and non processed pixels e Offset X specifies an amount of pixels to shift the second layer horizontally relative to the first layer e Offset Y specifies an amount of pixels to shift the second layer vertically relative to the first layer In addition to the controls at the bottom of the screen two additional buttons exist at the top of the screen that are unique to the Layer module e Open opens an image to load into t
82. should be set to 1 5 to make up for the red channels shorter exposure duration e Green Ratio adjusts a multiplier that should be applied to the green channel Note that top end clipping may occur as a result This value may be used to attain the exposure duration equivalent of the other channels e Blue Ratio adjusts a multiplier that should be applied to the blue channel Note that top end clipping may occur as a result This value may be used to attain the exposure duration equivalent of the other channels e Luminance File shows the path of the file that is used as the luminance channel Note a colour file used for this purpose will be converted to greyscale by adding up all pixel values no color space conversion is performed Red File shows the path of the file that is used as the red channel Note that if this file is a colour file then the red channel is extracted from this file e Green File shows the path of the file that is used as the green channel Note that if this file is a colour file then the green channel is extracted from this file e Blue File shows the path of the file that is used as the blue channel Note that if this file is a colour file then the blue channel is extracted from this file 36 StarTools 1 0 User Manual Levels Levels Overview The Levels module is typically one of the first modules to be used on raw stacked data Astronomical images are a bit different for terrestr
83. sizes by applying a Nyquist filter at the proper cut off frequency whereas low light mode typically forces a fixed ratio of 4 1 also Known as 2x2 binning and in some cases 16 1 also known as 4x4 binning When should you consider software binning You should consider software binning when your image s scale is bigger than is needed to reveal the smallest detail A typical example is an image that is recorded at a higher resolution than atmospheric seeing conditions permit In this case the image will seem blurry Reducing image size will reduce blur retain detail and reduce noise A common mistake is to retain too high a resolution during processing when the scale of the smallest detail simply does not warrant the extra resolution the image is said to be oversampled The redundant pixels may instrumental in reducing noise and improving the signal s fidelity at a smaller scale that matches the scale of the smallest achievable detail In a sense binning is the ultimate noise reduction tool Whereas any other noise reduction tools necessarily alter the image based on educated guesswork binning uses actual recorded but otherwise superfluous data to reduce noise Making the decision to perform binning very early on in the processing before stretching levels and or digital development will improve the signal you get to work with and prevent noise from propagating 10 A notable exception is when the imager intends to apply a dec
84. table parameters and settings Mode specifies the way the Contrast map should be applied DSO applies both light and dark corrections DSO Darken applies only corrections that darken the image DSO Lighten applies only corrections that lighten the image Finally Planetary Moon is a slightly milder alternative to the DSO mode more suitable for Planetary and Moon targets 32 StarTools 1 0 User Manual Contrast e Strength specifies the strength of the contrast correction where 0 specifies no correction and 100 specifies full correction Please note that when optimising the contrast of wide field images with lots of empty space Contrast may introduce artefacts in the darker parts of the image brightening some parts that should not be brightened To avoid such artefacts use the DSO Darken mode Also please note that similar to the Wipe module the Contrast module is susceptible to noise and may cause artefacts when presented with noisy images stacking artefacts dead pixels and or hot pixels 33 StarTools 1 0 User Manual LRGB LRGB Overview The LRGB module is a flexible colour image compositor It allows you to mix and match Luminance Red Green and or Blue images LRGB features automatic colour interpolation to make up for any missing channels This feature is particularly useful when for example creating a composite from Ha and Hb data in the red and blue channels LRGB will automatically gener
85. the processed image and retaining the image as it was before the module was invoked All modules typically have a Keep button which returns to the main screen keeping the image as it was processed by the module Some modules have preset buttons Clicking these buttons quickly recall useful default settings These buttons are distinguished by their icon they carry the same icon as their parent module in the main screen Some modules have a Mask button which invokes the mask editor Masking is a very powerful feature and pivotal to using most modules effectively greatly expands the amount of tools at your disposal It is highly recommended that the user get acquainted with its operation Modules that have a Mask button will also blink the current active mask 3 times when the module is first invoked This acts as a quick reminder of which pixels will be processed by the module according to the mask set For more information on how to use masks effectively please see the Masks chapter page 112 16 StarTools 1 0 User Manual Modules E pan Mask Cancel Keep Help Illustration 5 The Sharp module performing background processing Modules that perform background processing while the user remains free to tweak parameters will display a processing icon in the form of two cogs in the lower right corner of the image for example as seen in Illustration 5 This icon signifies that backgrou
86. throughout the image We are now ready to use this selection of pixels in another module the Layer module 124 StarTools 1 0 User Manual Masks fala StarTools a e StarTools Mask Cancel Open Swap Clone Keep Help Illustration 77 The Layer module We now launch the Layer module see Illustration 77 The Layer module see page 96 allows us to layer one image on top of the other in a manner specified by its parameters We will use this module to layer a blurred version of the original image on top of the original image but only for those pixels in our noise mask that are set leaving the good pixels intact and unblurred To accomplish this we click on the Clone button to clone the original noisy image into the second layer the middle image Doing so will once again show us the noise mask by blinking it three times in rapid succession 125 StarTools 1 0 User Manual Masks StarTools 9 Mask Cancel Open Swap Clone Keep Help 1 0 pixels 1 0 pixels O pixels Illustration 78 The Layer module with cloned image and layered result The right image which is the result of the layering operation will not show improvement yet see Illustration 78 126 StarTools 1 0 User Manual Masks StarTools n Mask Cancel Open Swap Clone Keep Help 4 0 pixels 2 0 pixels pixels pixels Illustration 79 The Layer module with cloned image and result with G
87. tion Illustration 44 An image of M42 suffering from severe axial also known as longitudinal chromatic aberration the are clear purple halos visible around stars Image courtesy of Roger Groom While somewhat more laborious the process outlined in this example yields a much superior result to the various generic defringer de halo and chromatic aberration scripts that are available for photo processing suites like PhotoShop and The Gimp This is especially the case for stars embedded in DSOs 85 StarTools 1 0 User Manual Boost OB StarTools A ea Os Before Y Illustration 45 Setting Boost s Filter Mode to Reject Notice the location of the mouse cursor Set Boost s Filter Mode to Reject as in Illustration 45 and position the mouse cursor on top of a sample of the halo colour we d like to remove 86 StarTools 1 0 User Manual Boost SO startools Cancel Reset Undo Mask Keep Help Illustration 46 The result after a few clicks of the mouse Any undesirable colours around the stars should be gone Simply click on the mouse a few times to attenuate the colour selected until no more purple fringing can be seen Your image should look similar to the one in Illustration 46 We don t worry about other parts of the image being affected at this point as is clearly the case For now it s only of importance that the stars look halo free Click the Keep button to keep the res
88. ts nimica a a ulaniness a coudabuiananst catia eves d enenleeaneutets Wats 132 StarTools 1 0 User Manual Introduction Introduction Thank you for your interest in StarTools StarTools is a astronomical image post processing program for Windows MacOSX and Linux StarTools sets itself apart from other processing software by focusing on the unique needs of amateur sidewalk astronomer in urban areas StarTools tries to make up for a lack of professional equipment and imaging in less than ideal urban skies It does this by leveraging the abundance of cheap 64 bit CPU power and memory as well as powerful off the shelf imaging hardware such as Compact Digital Cameras Digital Single Lens Reflex cameras and webcams Consequently StarTools contains features and algorithms that are not commonly found in software packages solely meant for professionals with the latter type of astronomers typically having access to semi professional equipment and dark sky sites StarTools can be used to post process a stacked image from start to finish or may be used as part of a greater toolchain of image processing programs Besides various unique and novel algorithms StarTools also aims to offer equivalents of most of the various PhotoShop actions available on the web all without the need to separately purchase a PhotoShop plug in compatible host program The StarTools project was created for the love astronomy and the desire to greatly lower the
89. ult and Save this image to a temporary file We will use this file at a later stage After saving click Undo to pull up the original unmodified image again 87 StarTools 1 0 User Manual Boost sr gt StarTools Cancel Do e Illustration 47 Using the Mask editor and its Auto option to create a star mask with only the brightest stars selected Next using the original unprocessed image we create a star mask containing only the brightest stars as it is only these stars that will suffer from the chromatic aberration To create the mask go into the Mask editor and select Auto Set the Selection Mode to Highlights gt Threshold and Threshold to something slightly lower than 100 The interface should look similar to that of Illustration 47 88 StarTools 1 0 User Manual Boost y A _ Open Save Auto Clear Invert Shrink Grow Undo Cancel Keep Help j o y de Illustration 48 Deselecting parts of the image that are not stars The Auto option may have selected parts of the image that are not stars for example in the image of Illustration 48 where the core of M42 has also been selected since it too was brighter than the threshold we set in the Auto feature Simply deselect any of such features by clicking on them before proceeding 89 StarTools 1 0 User Manual 90 StarTools 1 0 User Manual Boost ula Mask Cancel Keep Help Illustration
90. we require a few more pixels around the stars in our Mask Therefore we click the Grow button a few times and end up with as screen similar to the one in Illustration 61 105 StarTools 1 0 User Manual Layer Ea StarTools a gt StarTools Mask Cancel Open Swap Clone Keep Help Illustration 62 Launching the Layer module with the Keyhole Nebula image loaded We now launch the Layer module as can be seen in Illustration 62 106 StarTools 1 0 User Manual Layer 5 StarTools 2 Mask Cancel Open Swap Clone Keep Help A StarTools 1 0 pixels 1 0 pixels O O pixels Illustration 63 The Keyhole Nebula in the Layer module after cloning the image into the 2nd layer using the Clone button In the Layer module we Clone the image into the 2 layer by pressing the Clone button and end up with a screen similar to Illustration 63 107 StarTools 1 0 User Manual Layer StarTools 2 Mask Cancel Open Swap Clone Keep Help StarTools Illustration 64 After setting Mode to Darken and adjusting Offset X and Offset Y we end up with nice round stars We now set the Mode to Darken We then keep adjusting the Offset X and Offset Y parameters until the stars look nice and round similar to the screen in Illustration 64 We don t worry about any artefacts around the stars at this stage 108 StarTools 1 0 User Manual

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